Variable area exhaust mixer for a gas turbine engine

ABSTRACT

A variable area exhaust mixer is provided for a gas turbine engine. The variable area exhaust mixer includes an outer wall with a multiple of doors. Each of the multiple of doors is operable to control a passage entrance into at least one of a multiple of circumferentially arrayed vanes with a respective strut flow passage which essentially alters its bypass ratio during flight to match requirements.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. patent application Ser. No.14/595,570 filed Jan. 13, 2015, which claims priority to U.S.Provisional Patent Application No. 61/926,671 filed Jan. 14, 2014, whichare hereby incorporated herein by reference in their entireties.

BACKGROUND

The present disclosure relates to variable cycle gas turbine engines,and more particularly to an exhaust mixer therefor.

Variable cycle gas turbine engines power aircraft over a range ofoperating conditions, yet achieve countervailing objectives such as highspecific thrust and low fuel consumption. The variable cycle gas turbineengine essentially alters its bypass ratio during flight to matchrequirements. This facilitates efficient performance over a broad rangeof altitudes and flight conditions to selectively generate high thrustfor conditions requiring maximum propulsion, e.g., takeoff or maneuvers,and optimized fuel efficiency for cruise and loiter operation.

An exhaust nozzle controls the thermodynamic cycle of the gas turbineengine and enhances the thrust produced by the gas turbine engine flowstream. In variable cycle gas turbine engines, the size of the exhaustnozzle may need to vary considerably to accommodate large changes in thecycle and the individual flow streams may require a variable nozzle tomaximize performance and efficiency.

SUMMARY

A variable area exhaust mixer for a gas turbine engine, according to onedisclosed non-limiting embodiment of the present disclosure, includes anouter wall with a multiple of doors. Each of the multiple of doors isoperable to control a passage entrance to a strut flow passage within atleast one of a multiple of circumferentially arrayed vanes.

In a further embodiment of the present disclosure, each of the multipleof doors hinge inward toward the multiple of circumferentially arrayedvanes.

In a further embodiment of any of the foregoing embodiments of thepresent disclosure, each of the multiple of doors hinge inward towardeach respective circumferentially arrayed vane of the multiple ofcircumferentially arrayed vanes.

In a further embodiment of any of the foregoing embodiments of thepresent disclosure, each of the multiple of doors hinge about an axisgenerally parallel to a longitudinal engine axis of a gas turbineengine.

In a further embodiment of any of the foregoing embodiments of thepresent disclosure, each of the multiple of circumferentially arrayedvanes includes at least one trailing edge flap operable to control apassage exhaust from the respective strut flow passage.

In a further embodiment of any of the foregoing embodiments of thepresent disclosure, each of the trailing edge flaps hinge about an axisgenerally transverse to a longitudinal engine axis of the gas turbineengine.

In a further embodiment of any of the foregoing embodiments of thepresent disclosure, at least one of the multiple of circumferentiallyarrayed vanes includes one or more spraybars from a fuel manifold toselectively direct fuel through the multiple of circumferentiallyarrayed vanes to provide thrust augmentation.

In a further embodiment of any of the foregoing embodiments of thepresent disclosure, each of the multiple of circumferentially arrayedvanes includes a respective trailing edge flap operable to control apassage exhaust from the respective strut flow passage. Each of thetrailing edge flaps hinge about an axis generally transverse to alongitudinal engine axis of the gas turbine engine. Each of the multipleof doors hinge about an axis generally parallel to the longitudinalengine axis of a gas turbine engine.

In a further embodiment of any of the foregoing embodiments of thepresent disclosure, each of the multiple of doors hinge inward towardeach respective circumferentially arrayed vane of the multiple ofcircumferentially arrayed vanes.

A variable cycle gas turbine engine, according to another disclosednon-limiting embodiment of the present disclosure, includes a variablearea exhaust mixer between a third stream fan flow path and a core flowpath. The variable area exhaust mixer is operable to control flow fromthe third stream fan flow path to the core flow path through a multipleof circumferentially arrayed vanes.

In a further embodiment of any of the foregoing embodiments of thepresent disclosure, a second stream fan flow path is included radiallyinboard of the third stream fan flow path and radially outboard of thecore flow path.

In a further embodiment of any of the foregoing embodiments of thepresent disclosure, the second stream fan flow path and the third streamfan flow path is downstream of a fan section.

In a further embodiment of any of the foregoing embodiments of thepresent disclosure, the variable area exhaust mixer includes a multipleof doors. Each of the multiple of doors is operable to control a passageentrance into at least one of the multiple of circumferentially arrayedvanes with a respective strut flow passage.

In a further embodiment of any of the foregoing embodiments of thepresent disclosure, each of the multiple of doors hinge about an axisgenerally parallel to a longitudinal engine axis of a gas turbineengine.

In a further embodiment of any of the foregoing embodiments of thepresent disclosure, each of the multiple of circumferentially arrayedvanes includes a respective trailing edge flap operable to control apassage exhaust from the respective strut flow passage.

In a further embodiment of any of the foregoing embodiments of thepresent disclosure, each of the trailing edge flaps hinge about an axisgenerally transverse to a longitudinal engine axis of the gas turbineengine.

In a further embodiment of any of the foregoing embodiments of thepresent disclosure, at least one of the multiple of circumferentiallyarrayed vanes includes one or more spraybars from a fuel manifold todirect fuel through the multiple of circumferentially arrayed vanes toselectively inject fuel to provide thrust augmentation.

In a further embodiment of any of the foregoing embodiments of thepresent disclosure, a tail cone is included radially inboard of themultiple of circumferentially arrayed vanes.

A method of operating a gas turbine engine, according to anotherdisclosed non-limiting embodiment of the present disclosure, includesselectively changing an area-ratio between a fan flow in a third streambypass flow path and a core flow through a core flow path downstream ofa turbine section.

In a further embodiment of any of the foregoing embodiments of thepresent disclosure, the method includes selectively changing thearea-ratio by about 20%-50%.

The foregoing features and elements may be combined in variouscombinations without exclusivity, unless expressly indicated otherwise.These features and elements as well as the operation thereof will becomemore apparent in light of the following description and the accompanyingdrawings. It should be understood, however, the following descriptionand drawings are intended to be exemplary in nature and non-limiting.

BRIEF DESCRIPTION OF THE DRAWINGS

Various features will become apparent to those skilled in the art fromthe following detailed description of the disclosed non-limitingembodiment. The drawings that accompany the detailed description can bebriefly described as follows:

FIG. 1A is a general schematic view of an example fixed cycle(two-stream) gas turbine engine according to one non-limitingembodiment;

FIG. 1B is a general schematic view of an example variable cycle (threestream) gas turbine engine according to another non-limiting embodiment;

FIG. 2 is a perspective view of a variable area exhaust mixer in an openposition according to one non-limiting embodiment;

FIG. 3 is a perspective view of one vane of the variable area exhaustmixer in an open position;

FIG. 4 is a lateral cross section of the vane of FIG. 3;

FIG. 5 is an a lateral cross-section of a vane according to anothernon-limiting embodiment; and

FIG. 6 is a perspective view of the variable area exhaust mixer in aclosed position; and

FIG. 7 is a perspective view of one vane of the variable area exhaustmixer in a closed position.

DETAILED DESCRIPTION

FIGS. 1A and 1B schematically illustrate example architectures for a gasturbine engine 10. The gas turbine engine 10 is disclosed herein as afixed cycle (two-stream architecture; FIG. 1A) or a variable cycle(three-stream architecture; FIG. 1B). Each gas turbine engine 10 is amulti-spool turbofan that generally includes a fan section 12, a highpressure compressor section 14, a combustor section 18, a high pressureturbine section 20, a low pressure turbine section 22, a turbine exhaustcase section 24, an augmentor section 26, an exhaust duct section 28 anda nozzle section 30 along a central longitudinal engine axis A. Althoughdepicted with specific architectures in the disclosed non-limitingembodiments, it should be understood that the concepts described hereinare not limited to only the illustrated architectures.

A low spool 34 and a high spool 36 rotate about the engine centrallongitudinal axis A relative to an engine case structure 48. The lowpressure turbine section 22 of the low spool 34 drives the fan section12 directly or through a geared architecture 32 to drive the first stageof fan section 12 at a lower speed than subsequent stages. Examplegeared architectures 32 include an epicyclic transmission, namely aplanetary or star gear system, that may be located in various enginesections such as forward of the high pressure compressor section 14 oraft of the low pressure turbine section 22.

The engine case structure 48 generally includes an outer case structure50, an intermediate case structure 52 and an inner case structure 54(all illustrated somewhat schematically). Various static structuresindividual or collectively form the case structure 48 to essentiallydefine an exoskeleton that supports rotation of the spools 34, 38.

In the fixed cycle (two-stream architecture; FIG. 1A), the fan section12 communicates airflow into a second stream bypass flow path 58 and acore flow path 60. In the variable cycle (three-stream architecture;FIG. 1B), the fan section 12 communicates bypass flow into a thirdstream bypass flow path 56 as well as the second stream bypass flow path58 and the core flow path 60. The third stream bypass flow path 56 isgenerally annular in cross-section and defined by the outer casestructure 50 and an additional intermediate case structure 53 (see FIG.1B). The second stream bypass flow path 58 is also generally annular incross-section and defined by the intermediate case structure 52 and theinner case structure 54. The core flow path 60 is generally annular incross-section and defined by the inner case structure 54. The secondstream bypass flow path 58 is defined radially inward of the thirdstream bypass flow path 56 and the core flow path 60 is radially inwardof the second stream bypass flow path 58. Various crossover andcross-communication flow paths may alternatively or additionally beprovided to provide control of the flow streams, bypass ratio, and thusengine cycle.

The second stream bypass flow path 58 may include a flow controlmechanism 62 (illustrated schematically) of various configurations suchas electrical, pneumatic or mechanically operated blocker doors thatoperate as a throttle point. The flow control mechanism 62, either aloneor in combination with other control mechanisms, is selectively operableto control airflow through the second stream bypass flow path 58.

The core flow is further compressed by the high pressure compressorsection 14, mixed and burned with fuel in the combustor section 18, thenexpanded through the high pressure turbine section 20 and the lowpressure turbine section 22. The turbines sections 20, 22 rotationallydrive the respective spools 34, 38 in response to the expansion. Itshould be further appreciated that other architectures such as athree-spool architecture will also benefit herefrom.

Downstream of the turbine sections 20, 22 the exhaust duct section 28may be circular in cross-section as typical of an axisymmetric augmentedlow bypass turbofan or may include non-axisymmetric cross-sectionsegments. In addition to the various cross-sections, the exhaust ductsection 28 may be non-linear with respect to the central longitudinalengine axis A to form, for example, a serpentine shape to block directview to the turbine sections. In addition to the various cross-sectionsand the various longitudinal shapes, the exhaust duct section 28 mayterminate in the nozzle section 30 such as a convergent-divergent,non-axisymmetric, two-dimensional (2D) vectorable, or other nozzlearrangement architectures.

In the fixed cycle (two-stream architecture; FIG. 1A), the exhaustnozzle section 30 (illustrated schematically) receives a mixed flow 66from the second stream bypass flow path 58 and the core flow path 60combined by the exhaust mixer 70. In the variable cycle (three-streamarchitecture; see FIG. 1B), the nozzle section 30 may also include aradially outboard third stream exhaust nozzle 64 (illustratedschematically). The third stream exhaust nozzle 64 may be of variousnozzle architectures.

The variable area exhaust mixer 70 (also shown in FIG. 2) may be locatedupstream or adjacent a convergent region 68 within the exhaust ductsection 28. That is, the variable area exhaust mixer 70 is axiallylocated at an exhaust mixing plane where the second stream bypass flowpath 58 joins the core flow path 60 to modulate bypass and core flowstream mixing. As the second stream bypass flow path 58 is generally atonly a relatively slightly higher pressure than the flow stream from thecore flow path 60, the variable area exhaust mixer 70 facilitatesinjection of the fan flow stream into the relatively high pressure coreflow stream. The relatively high velocity of the core flow streamthrough the exhaust mixer 70 facilitates this injection by lowering thestatic pressure in the core stream 60 as it passes through the exhaustmixer 70.

In the variable cycle (three-stream architecture; see FIG. 1B), thevariable area exhaust mixer 70 is axially located at the exhaust mixingplane to mix the fan flow stream from the third stream bypass flow path56 with the core flow stream of the core flow path 60. As the thirdstream bypass flow path 56 is generally at only a relatively slightlyhigher pressure or even lower pressure than the flow stream from thecore flow path 60, the variable area exhaust mixer 70 facilitatesinjection of the fan flow stream into the relatively high pressure coreflow stream. The relatively high velocity of the core flow streamthrough the exhaust mixer 70 facilitates this injection by lowering thestatic pressure in the core stream 60 as it passes through the exhaustmixer 70.

With reference to FIG. 2, the variable area exhaust mixer 70 includes amultiple of circumferentially arrayed and radially extending vanes 72.The multiple of circumferentially arrayed vanes 72 may extend betweenthe inner case structure 54 and the intermediate case structure 52. Inone disclosed non-limiting embodiment, the intermediate case structure52 terminates with an outer wall 76 of the variable area exhaust mixer70 and the inner case structure 54 terminates with a tail cone 74.

The outer wall 76 of the variable area exhaust mixer 70 includes amultiple of doors 78 each of which controls a passage entrance 80 to aplenum 81 that is open to a strut flow passage 82 formed through each ofthe respective vanes 72. In one disclosed non-limiting embodiment, eachof the multiple of doors 78 hinges inward into the plenum 81 about arespective axis D generally parallel to the central longitudinal engineaxis A. It should be appreciated that door arrangements such as slidingdoors may alternatively or additionally be utilized. In this disclosednon-limiting embodiment, each two (2) of the multiple of doors 78 arelocated radially outbound of each strut flow passage 82 to provide aninwardly directed rectilinear ramped passage entrance 80 to provide arelatively large flow area for the fan flow stream(s). The multiple ofdoors 78 thereby provide significant flow capacity that selectivelyincreases the bypass area-ratio between the fan flow stream and the coreflow stream when the variable area exhaust mixer 70 is open.

With reference to FIG. 3, each of the multiple of circumferentiallyarrayed vanes 72 include first and second walls 84, 86, joined at aleading edge 88 and a trailing edge 90 to define the strut flow passage82. The first and second walls 84, 86 may form an airfoil or otheraerodynamic shape.

At least one of the first and second walls 84, 86 of each of themultiple of circumferentially arrayed vanes 72 includes a trailing edgeflap 92. When the trailing edge flap is closed an aerodynamic vane shapeis formed to minimize pressure flow loss for core flow stream passagethrough the variable area exhaust mixer 70. The trailing edge flap 92 isselectively opened to form a passage exhaust 94 from the respectivestrut flow passage 82 (also shown in FIGS. 4 and 5).

The trailing edge flap 92 may be hinged along an axis F with respect toone of the first and second walls 84, 86 (FIG. 4) or, alternatively,from both of the first and second walls 84, 86 to form as a split flaparrangement (FIG. 5). In these disclosed non-limiting embodiments, theaxis F is generally transverse to the axis D and the longitudinal engineaxis A. The multiple of doors 78 and respective trailing edge flaps 92are selectively operable to form a relatively large area flowpathbetween the fan stream flow path 56 or 58 and the core flow path 60 forhigh bypass operations.

When open, the variable area exhaust mixer 70 substantially changes thearea-ratio between the fan flow path(s) 56, 58 and the core flow path60. Furthermore, the generally transverse arrangement of the multiple ofdoors 78 to the multiple of trailing edge flaps 92 of the variable areaexhaust mixer 70 facilitates uniform mixture and redirection of the fanflow stream(s) from the fan flow path(s) 56, 58 radially inward thenaxially aftward along the longitudinal engine axis A to provide mixinguniformity with minimum mixing pressure loss. The multiple ofcircumferentially arrayed vanes 72 further facilitate uniform radialmixing of the fan flow stream to increase propulsive efficiency as therelatively uniform mixing of the relatively cool air from the fan flowstream with the relatively hot core combustion products of the core flowstream downstream of the low pressure turbine section 22 providesincreased propulsion efficiency and reduced exhaust jet noise.

In one operational example, the variable area exhaust mixer 70 isoperable to change the area-ratio between the fan flow stream and thecore flow stream by about 20%-50%. In other words, during high bypassoperation, the variable area exhaust mixer 70 is opened (FIGS. 3, 4, 5)from a closed position (FIGS. 6 and 7) to increase the bypass ratio byabout 20%-50%.

The multiple of doors 78 and the respective trailing edge flaps 92 ofthe variable area exhaust mixer 70 may be selectively actuated viaelectric actuators, pneumatic actuators, mechanical actuators, orcombinations thereof to alter the bypass ratio during flight to matchrequirements. This facilitates efficient performance over a broad rangeof altitudes and flight conditions to generate high thrust forhigh-energy maneuvers yet optimize fuel efficiency for cruise and loiteroperations.

The augmentor section 26 may be located downstream of the variable areaexhaust mixer 70, or alternatively, may be integrated into therespective multiple of circumferentially arrayed vanes 72 to selectivelyprovide thrust augmentation with the oxygen-rich fan flow stream. Inthis disclosed non-limiting embodiment, one or more of the multiple ofcircumferentially arrayed vanes 72 may contain one or more spraybars 100from a fuel manifold 102 within the tail cone 74 to selectively sprayfuel for thrust augmentation through the first and/or second walls 84,86. The relatively low velocity flow stream from the multiple of vanes72, in combination with their rear-facing trailing edges 90 thereof arereadily configured to provide bluff body flame holders to generate a lowvelocity region in the exhaust flow stream to facilitate flame stabilityfor the augmentor section 26.

The variable area exhaust mixer 70 provides substantial benefits infuel-burn, range, and performance by facilitation of an engine cyclewith a variable bypass ratio that can be integrated with thrustaugmentation features to provide an adaptive, multi-functional, variableexhaust systems for various propulsion systems. The variable areaexhaust mixer 70 also facilitates noise reduction though a decrease inthe exhaust jet temperature and velocity and efficient mixture of thefan and core flow streams with a significant range of variability inarea ratio. The variable area exhaust mixer 70 is also compact andreadily integrates with a turbine exhaust case and vehicle nozzle toreduce system weight, which otherwise trades with mixing efficiency andlosses.

It should be understood that relative positional terms such as“forward,” “aft,” “upper,” “lower,” “above,” “below,” and the like arewith reference to the engine but should not be considered otherwiselimiting.

Although the different non-limiting embodiments have specificillustrated components, the embodiments of this invention are notlimited to those particular combinations. It is possible to use some ofthe components or features from any of the non-limiting embodiments incombination with features or components from any of the othernon-limiting embodiments.

It should be understood that like reference numerals identifycorresponding or similar elements throughout the several drawings. Itshould also be understood that although a particular componentarrangement is disclosed in the illustrated embodiment, otherarrangements will benefit herefrom.

Although particular step sequences are shown, described, and claimed, itshould be understood that steps may be performed in any order, separatedor combined unless otherwise indicated and will still benefit from thepresent disclosure.

The foregoing description is exemplary rather than defined by thefeatures within. Various non-limiting embodiments are disclosed herein,however, one of ordinary skill in the art would recognize that variousmodifications and variations in light of the above teachings will fallwithin the scope of the appended claims. It is therefore to beunderstood that within the scope of the appended claims, the disclosuremay be practiced other than as specifically described. For that reasonthe appended claims should be studied to determine true scope andcontent.

What is claimed is:
 1. A variable cycle gas turbine engine, comprising:a variable area exhaust mixer between a third stream fan flow path and acore flow path; the variable area exhaust mixer operable to control flowfrom the third stream fan flow path to the core flow path through amultiple of circumferentially arrayed vanes.
 2. The variable cycle gasturbine engine of claim 1, further comprising a second stream fan flowpath radially inboard of the third stream fan flow path and radiallyoutboard of the core flow path.
 3. The variable cycle gas turbine engineof claim 2, wherein the second stream fan flow path and the third streamfan flow path is downstream of a fan section.
 4. The variable cycle gasturbine engine of claim 1, wherein the variable area exhaust mixerincludes a multiple of doors; and each of the multiple of doors isoperable to control a passage entrance into at least one of the multipleof circumferentially arrayed vanes with a respective strut flow passage.5. The variable cycle gas turbine engine of claim 1, wherein each of themultiple of doors hinge about an axis generally parallel to alongitudinal engine axis of a gas turbine engine.
 6. The variable cyclegas turbine engine of claim 5, wherein each of the multiple ofcircumferentially arrayed vanes includes a respective trailing edge flapoperable to control a passage exhaust from the respective strut flowpassage.
 7. The variable cycle gas turbine engine of claim 6, whereineach of the trailing edge flaps hinge about an axis generally transverseto a longitudinal engine axis of the gas turbine engine.
 8. The variablecycle gas turbine engine of claim 1, wherein at least one of themultiple of circumferentially arrayed vanes includes one or more spraybars from a fuel manifold to direct fuel through the multiple ofcircumferentially arrayed vanes to selectively inject fuel to providethrust augmentation.
 9. The variable cycle gas turbine engine of claim1, further comprising a tail cone radially inboard of the multiple ofcircumferentially arrayed vanes.
 10. A method of operating a gas turbineengine comprising selectively changing an area-ratio between a fan flowin a third stream bypass flow path and a core flow through a core flowpath downstream of a turbine section.
 11. The method of claim 10,further comprising selectively changing the area-ratio by about 20%-50%.